Molecular basis of RNA function

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RNA plays a fundamental key role in life as a variety of regulatory and catalytic molecules involved in gene expression and cellular regulation. Here, we have studies molecular bases of dynamic RNA functions by focusing on RNA-protein complexes, regulatory RNAs for gene expression, splicing, transport and translation. The remarkable progress in functional and structural biology of translational apparatus has uncovered a novel biological phenomenon of macromolecular mimicry between protein and tRNA. The 3D struetures of translational elongation factor EF-G and ribosome recycling factor RRF are shown to mimic a tRNA shape. Another, even more sophisticated, example may be polypeptide release factors that are shown to possess a tripeptide 'anticodon' to decipher stop codons in mRNA, showing an impressive mimic of tRNA function. It is surprising that it took 4 decades since the discovery of the genetic code to figure out the basic mechanisms behind the deciphering of its 64 codons. Other achievements in the translational control - such as mammalian frameshift control, trans-translation with tmRNA in bacteria, and cell proliferation induced by the abnormality in the mammalian translation initiation factors - as well as in mRNA export, RNA-binding proteins involved in cell differentiation and RNA-protein complex structures, have uncovered numerous novel mechanisms of gene expression and RNA functions. These accomplishments clearly emphasized the biological importance and interest of the regulatory role of RNA and the mechanisms underlying the post-transcriptional control of gene expression. Certainly, understanding of RNA information flow has increasing importance in the post-genome era. A future emerging understanding of spatiotemporal networking of diverse functional RNAs Will greatly facilitate post-genome research as well as structural biology, while expanding our knowledge of how deeply and universally RNA constitutes life.